Polyethylene glycol-enwrapped silicon carbide nanowires network/expanded vermiculite composite phase change materials: Form stabilization, thermal energy storage behavior and thermal conductivity enhancement

Polyethylene glycol (PEG)-enwrapped silicon carbide nanowires (SiC NWs) network/expanded vermiculite (EVM) form-stable composite phase change materials (PSE fs-CPCMs) were prepared to overcome the disadvantage of form instability during phase transition and improve the slow heat transfer rate of PEG. The flowability was effectively solved by synergy between the pore structures of EVM and surfaces of SiC NWs. PSE3.29 exhibited the maximum adsorption ratio of PEG as high as 73.12 wt%. The heat transfer of PSE fs-CPCMs could be significantly enhanced by the SiC NWs filler, and the thermal conductivity of PSE3.29 reached 0.53 W/m K, which was 8.8 times higher than PEG. Theoretical calculation methods were applied to evaluate the thermal conductivity enhancement ability of SiC NWs. Maxwell-Eucken model (MEM) predicted obviously higher thermal conductivity enhancement than the experimental results due to stronger dependent on lower volume fraction of disperse phase. The prediction results obtained with effective medium percolation theory (EMPT) were in reasonable agreement with experimental values. Thermal energy storage behavior of PSE fs-CPCMs were strongly affected by the confinement effect of nanoscale pore structures of EVM and surface interactions of EVM and SiC NWs. FT-IR, TGA and phase change cycles test results confirmed that the PSE fs-CPCMs exhibited excellent chemical compatibility, thermal stability and reliability.